Portable belt-driven power handsaw



March 1954 A. w. RICHARDS ET AL ,4

PORTABLE BELT-DRIVEN POWER HANDSAW 5 Sheets-Sheet 1 Filed Feb. 2, 195CMIN 0 TL? 9 5 Q EE. 5 k? .2 V

March 1954 A. w. RICHARDS ET AL 2,671,47

PORTABLE BELT-DRIVEN POWER HANDSAW Filed Feb. 2, 1950 5 Sheets-Sheet 2JNVI ENTORS. flrc/zer IMF/(bards A m); JOs/er/zus.

7/267 1477-0 lM/E/ March 9, 1954 A. w. RICHARDS ET AL 2, 7 ,475

PORTABLE BELT-DRIVEN POWER HANDSAW 5 Sheets-Sheet 3 Filed Feb. 2, 1950.5 m; Q M M M J C r 77 firm, 4, 3 m 7 Y2 B March 9; 1954 A. w. RICHARDSET AL PORTABLE BELT-DRIVEN POWER HANDSAW 5 Sheets-Sheet 4 Filed Feb. 2.1950 Y frwhc/ Ower/xas. wfmlnwiwir March 1954 A. w. RICHARDS ET AL ,6 7

PORTABLE BELT-DRIVEN POWER HANDSAW Filed Feb. 2, 1950 5 Shee'ts-Sheet 5Patented Mar. 9, 1954 PORTABLE BELT-DRIVEN POWER HANDSAW Archer W.Richards, Chagrin Falls, and Ervin J. Osterhus, Cleveland, Ohio,assignors to Syntron Company, Homer City, Pa., a corporation of DelawareApplication February 2, 1950, Serial No. 142,066

3 Claims.

This invention relates generally to motor operated portable hand saws,and more particularly to belt-driven hand saws.

Motor operated belt-driven hand saws have been suggested in the art asdisclosed in Wertz, 1,863,486, of March 20, 1928, yet this saw was notsuccessful commercially probably owing to the impracticability of itsstructure and design. It is obviously too heavy and bulky and dimcult tomanipulate. The center of mass is not properly located relative to thehandle. It shows an induction motor the speed of which is less than thatof the saw requiring a step-up transmission. A gear-driven motor handsaw was much smaller and very neat in design. The gear saw became verypopular, yet the gears wear out in a relatively short time and they arequite noisy.

The motor operated belt-driven hand saw comprising this inventionprovides a higher speed series motor that is light in weight and readilymanipulatable. The speed is reduced to the saw which is quiet andefficient in its operation. The structure of this novel hand saw permitsit to cut in a plane disposed angular to the side of the saw and to thesurface of the board being cut. The base of this saw may also beadjusted to determine the depth of the saw cut, all of which makes thishand saw less dangerous to handle.

This compact belt-driven hand saw provides a long lubricant-packed shaftwith the saw blade on one end and a double grooved pulley on the otherend for using two V-belts to drive the saw. Two V-belts are employedowing to the close proximity of the motor and saw shaft and the smallmotor driving pulley which provides only a short arcuate belt engagingsurface. These structural features provide long life with durability andpermit the transmission of adequate power to the saw blade for properlyperforming its work. The gear type drive is inadequate for thetransmission of power and even at light loads it soon wears out.

This belt-driven hand saw is provided with spaced cradle sockets forsupporting the motor. The surfaces on the motor which are received inthe cradle sockets are eccentric to its rotary shaft. Thus, a slightturn of the motor housing in its sockets increases or decreases thedistance between the motor shaft and the blade shaft to enable one toadjust the tension on the belt drive.

Another structural characteristic of this beltdriven hand saw is thedisposition of the two handles relative to the center of mass. The

2 motor shaft and the saw blade shaft are parallel and the principalhandle is above and slightly in back of the motor which is the heaviestpart. A hand knob is located above and slightly forward of the sawshaft. This arrangement properly distributes the Weight of the toolmaking it very easily handled and manipulated.

Another object is the provision of spring means by which constanttension of the belt may always be uniformly measured and adjustedregardless of wear.

Another object is the provision of a belt-driven hand saw wherein themotor and saw shafts are parallel and close together making a compacttool.

Another object of this invention is the provision of a simple structurethat is economical to manufacture. The stampings forming the tool baseand the wood engaging surface together with the several parts of thehousing are simple structures readily assembled. The motor being mountedunder the housing, needs no heavy exterior shell. It is in the form oftwo deeply drawn cups having sockets for receiving the shaft bearingsand the arcuate eccentric supporting surfaces are secured on the ends ofthese cups by welding. The motor is held by a strap which may beloosened to shift the motor and tighten the belt.

A long sleeve bearing is employed to rotatably support the saw shaft.This hearing may be packed and thus be sealed off. The long bear ingadds many more hours of life to the saw as it properly resists lateralshock such as experienced when the saw first engages the material it isto cut or a hard spot during the cutting thereof.

Other objects and advantages appear in the following description andclaims.

The accompanying drawings show, for the purpose of exemplificationwithout limiting the invention or claims thereto, certain practicalembodiments of the invention wherein:

Fig. l is a plan view of the belt-driven hand saw comprising thisinvention;

Fig. 2 is a view in side elevation of the structure shown in Fig. 1;

Fig. 3 is a view in side elevation of the opposite or saw side of thehand tool;

Fig. 4 is a rear elevational view of the hand tool;

Fig. 5 is a sectional view of the saw and its arbor;

Fig. 6 is a plan view of the frame and adiustable base of the saw;

Fig. 7 is a view in side elevation of Fig. 6;

Fig. 8 is a view in horizontal section of a single belt drive with partsbeing broken away;

Fig. 9 is a view in vertical section of the structure shown in Fig. 8;

Fig. 10 is a view in horizontal section of a single cog belt drive withparts being broken away;

Fig. 11 is a view in vertical section of the structure shown in Fig. 10and Fig. 12 is a graph of the speed v. current load for the three typesof belt transmission, single V-belt, double V-belt and cog belt.

Referring to the drawings, it will be noted that the hand saw comprisingthis invention is made up of an adjustable base I which is hingedlyattached to the base plate or frame member 2 that supports the seriesmotor a and the saw shaft 4. The frame member 2 also has the hous- I.guard 63.

The adjustable saw base I is shown more in detail in Figs. 6 and 7 andis provided with the aligned hinged sockets II and I2 for receiving theone leg of the hinge pin I3. The other leg er the hinge pin I3 ispivotally retained in the aligned hinge sockets I4 and I which arewelded to the rear end of the frame 2. In view of the fact that thesingle hinge pin I3 has two legs disposed at 90 to each other and sincethe hinge sockets II and I2 are secured to the base i, it is obviousthat the outer end of the base I may be swung on the axes of the socketsII and 52 toward and away from the frame 2 to provide a relative angularposition of the saw blade to the under surface of the base I. The sawhas to be turned in the proper direction to determin the direction ofthis outer cut relative to a plane normal to the underside of the baseI.

On the other hand, it is also noted that the front end of the base I maybe swung toward and away from the frame 2 as the base is also pivoted onthe other leg of the pin I3 that lies in the hinge sockets I4 and I5.With this adjustment the forepart of the base I is moved toward and awayfrom the saw and the rear part is held by the hinge pin in a fixedpivoted position relative to the saw. If the base I is close to theunderside of the frame 2 it will be parallel therewith and the front endmay be moved toward or away from the shaft 4 carrying the saw I0,thereby providing different depths of cut for the saw blade Ill. Both thangular and depth adjustment of the base I may be made simultaneouslyrelative to the saw blade.

A member I6 is pivotally hinged on the hinge pin I3 intermediate of thesockets I 4 and I5 and extends upwardly to support the clamping bolt I!which rides through the arcuate slot in the arcuate gauge plate I8 whichis provided with numerals indicating the angular degree of the underfaceof the base plate I relative to the saw. The bolt I1 is held in anydesired position in its arcuate slot by means of the winged clamping nutI9. The center of radius of th arcuate slot is of course taken from theaXis of the. sockets II and I2.

A member 20 is provided with a socket 2| for receiving the outer endofthe hinge pin I3 adjacent the socket II. The member 253 extends upwardlyto receive the bolt 22 that is clamped in place by means of the nut 23.The bolt 22 is adjustable along the slot 24 in the gauge plate 4 25which is supported integrally relative to the housing 5 and the arcuateslot 24 has for its center of radius the axis of the sockets I4 and I5secured to the end of the frame 2. Thus, when the base is pivoted on theaxis of the sockets I4 and I5 and the front end swings downwardly todetermine the depth of the sawcut, it may be clamped in any desiredposition along the slot 24 so as to properly gauge the saw relative tothe undersurface of the base plate I.

The extreme front end of the bas plate I is turned upwardly to form alip 26 which permits the base to be slid over the wood or a series ofboards that might be rough or otherwise uneven in sawing the same, suchas sawing off the ends of the roof boards that project beyond the eaveof a house. A lateral gaug 28 is secured to a stem 29 that is marked asa scale and slides through the socket 30 and may be secured by the setscrew 3I. The relative position of the gauge 28 and the saw blade Illmay be set by shifting the stem 29 to a desired position and clampingthe same by means of the clamping screw 3I in the socket 30.

Referring again to Figs. 6 and 7, the base plate or frame 2.is providedwith oppositely disposed arcuate cradle surfaces 33 to receive the motor3. The parallel cradle surfaces are arranged to receive the tube 35which is shown in detail in Fig. 5 and contains two bearing sleevesections 31 and 38. Intermediate the bearing sleeves 31 and 33 anannular oil wick 36 is inserted and may be supplied with oil through theaxial and radial passages by removing the saw blad mounting screw 43which also closes the oil reservoir formed by the axial and radialpassages in the shaft 40. The bearing sleeves 31 and 38 have flangeswhich cover the ends of the tube 35. The saw shaft 40 is arranged torotate in the composite bearing sleeve mounted in the tube 35. A doublegrooved pulley 4| is secured to one end of the shaft 40 and a series offan blades 42 are on inner face of the pulley for the purpose ofcreating a draft to circulate air from the left side of the housing 5toward the saw to cool the pulley and prevent the deposit of sawdustwithin the housing. The fan prevents quiescence in the housing and anytime that sawdust tends to creep in it provides circulation fordischarging the same. In this manner the motor and other parts are keptclear of sawdust, yet they are not sealed in and are cooler inoperation.

The opposite end of the shaft 4 has the saw blade Ill secured thereto bymeans of the nut 43, the blade being held between the washers 44. Itwill be noted that the tube 35 extends beyond the upwardly extendingwall of the base 2 for the purpose of functioning to receive the hearingsleeve 45 to which is journaled the cover 8. The outer end of thebearing sleeve 45 has the movable shield 9 secured thereto, as indicatedat 46, and-is permitted to rotate about the axis of the saw. This shieldis provided with a spring, as indicated at 41, to keep the shield 9 inits fully extended position, as indicated in Fig. 3.

The motor 3 is a universal motor being series wound and operating at aspeed of approximately twelve thousand R. P. M. It is encased in twocup-like housings, three and three-fourths inch in diameter, as shown at48 and 49, which are shoved over the ends of the motor field and areprovided with flanges that come together, as indicatedat 50. Eachcup-shaped housing i id d. wit n.. 1 UP Q FH E fill i fl ei as shown atand 52, which are arranged to rest in the cradles 33 and 32,respectively, of the base 2. A strap member 53 is secured at one end tothe base 2, as shown at 54, and extends over the flanges 5B, and is alsoadjustably secured at its other end to the base 2, as indicated at 55,for the purpose of tightly clamping the motor down to the base 2. Themotor 3 has a condenser 39 to check radio interference and is likewiseprovided with a double-grooved pulley 56 approximately one andone-quarter inch in diameter for receiving the belt members 51 and 58that extend from the motor pulley to the saw pulley til which isapproximately two and one-half inches in diameter which providesapproximately 12,000 surface feet per minute for an eight inch sawblade. The arcuate supporting surfaces 5! and 52 are eccentric to theshaft of the motor and, thus, any relative arcuate adjustment of themotor will determine the tension on the belts 5? and 58. It is necessaryfor one to remove the cover 5 and loosen the strap 53 and shove againstthe spring 59 until it aligns with the mark 59' to rotate the motor to aposiiton where the tension on the belt is proper and in accordance withthe pressure of the flexed springs and then reclamped. This uniformtension on the belts may be made when the motor is stationary oroperating the saw. These mating arcuate cradle surfaces may be knurledor roughened to prevent the motor from slipping from its adjustedposition.

The principal housing 5 encases the whole of the motor and the majorityof the tube carrying the shaft :1 and has attached thereto the separatehousing 50 which encloses the belts. The housing 60 joins the housing 5to lock the latter in position and it is supported by the bracket 8iwhich is welded to the base 2. The housing 59 is held in place by thebolt 62, as shown in Fig. 1.

The grip handle 6 contains the electric switch actuated by the fingertrigger 64. It will be noted that the butt end 65 of the handle isattached to the rear of the housing 5 above and to the rear of the motor3; whereas the knob handle I is secured to the front of the housingahead of the sleeve l. This disposition of the handles properly placesthe center of mass between the handles 6 and 1 thereby permitting theoperator to readily manipulate the saw. The wires coming from thecurrent supply in the cable 66 pass into the handle 5 to the switch andthence back to the motor 3. It will be noted that the switch is a doublepole switch and both lines are open when the saw is turned on. A thirdwire in the cable may be used to ground the saw. The cable 66 isprovided with a ground wire that is connected to the inside of thehandle below the rubber cable bushing and may have a ground clip at itsother end.

The saw shaft 4 is parallel to and very close to the shaft of the motor3 to concentrate the weight directly under the handle 6. This provides avery compact saw with these shafts as close as the size of the pulleyspermit without requiring more than two belts. In the structure shown themotor 3 may be adjusted on the arcuate bearing surfaces so that the axesof the saw shaft and motor shafts are from three and one-quarter tothree and five-eighths inches apart. This provides three-eighths inchfor wear and belt adjustment. The saw shaft housing 35 may be spacedfrom the motor casing 48, 49 as little as two and three-eighths inchesto as much as four and one-half inches since the tubing '35 isapproximately one inch in outside diameter; whereas the casing 48, 49 isthree and three-quarter inches and the pulleys have a ratio ofapproximately two and one-half to one. These dimensions provideimportant factors in the makeup of this belt type portable saw.

In Figs. 8 and 9, a single V-belt i0 is used to transmit power from themotor 3 by the single grooved pulleys H and 12 on the series motor andsaw shafts respectively. The saw shaft pulley '12 has the cooling fan 42on its inner face to dissipate the frictional heat developed by the belt10. The driving and driven pulleys are the same size as pulleys 4i and56.

In Figs. 10 and 11 a single cog belt T3 is used to transmit power fromthe motor to the saw shafts. A cog pulley 14 is provided on the motorshaft and a cog wheel '55 is provided on the saw shaft 7 In thetransmission of power the cog belt has little or no friction losses ascompared to the single or double belt drive, yet all three drivesprovide smooth operation under load with a cushioning effect between thehigh torque series motor and the saw' blade. It is also possible to usegreater pulley ratios and a higher speed motor with the same diametersaw because there is no slippage with a cog belt. A smaller drivingpulley and closer centers between the saws and motor shafts may be usedwith a. cog belt which would be impossible with V-belts. However, thereare limitations such as the top no-load speed of a saw. A sawblade has acritical noload speed at which it will flutter and vibrate. This actionwill probably result in fatigue and. cracking. The no-load high speedflutter also causes a rough cutting at the start of the saw stroke whichis decidedly undesirable. A saw blade eight and one-half inches indiameter, which is employed on the saws disclosed herein, has a criticalflutter at no-load with speed of 7,200 B. P. M. and a definite flutterat 1.400 R. P. M.

The performance curves shown in Fig. 12 illustrate the different speedsattained for different loads from no-load to full-load. Curve 16 is thecog belt drive, 11 the single V-belt drive and 18 the double V-beltdrive. It will be noted that for the same series motor and diameter ofpulleys the cog belt drive provides a much higher noload speed. This isdue to the fact that there is no slip and the speed is way above theflutter speed. In order to use this cog belt drive, it would benecessary to increase the pulley ratios and lower the no-load speed.

The single V-belt drive also has a higher noload speed because thetransmission losses are not high and to use this transmission the pulleyratios would likewise have to be increased to bring the no-load speeddown. There is a limit to the size of the pulleys that can be employed.When the driving pulley cannot be made any smaller and the driven pulleycannot be made any larger without raising the saw shaft higher from thebase plate, then the depth of out has to be sacrificed. If a largerdiameter saw is required, then a more powerful motor is necessarythereby increasing the weight of the saw.

To avoid these difliculties the double V-belt drive provides the answer.This is shown by the curve 18. At no-load the efficiency is poor and thebest speed attainable for the same motor and the eight and one-half inchsaw blade is approximately 6,900 B. P. M. which is below the criticalflutter speed. However, at a load greater 7 than normal full load, thetransmission is sub-' stantially as efficient as the cog belt. Normalload is about ten amps. on these performance curves.

We claim:

1. A hand saw power tool consisting of a pressed metal base plate havingan upwardly extending perimetral flange, two sets of aligned arcuatecradle surfaces in oppositely disposed sections of said flange, the axesof said arcuate cradle surfaces of both sets being spaced apart andparallel to each other, a rotary motor having arcuate surfaces on theends thereof complementary to one set of said arcuate cradle surfacesand mounted therein for supporting said motor, the arcuate surfaces ofsaid motor being disposed eccentrically to the rotary axis of the motor,a sleeve secured in the other set of said arcuate cradle surfaces,spaced bearings mounted in said sleeve, a shaft rotatable in saidbearings and extending beyond the ends of said sleeve, a saw mounted onone end of said shaft, a pulley mounted on the other end of said shaft,a pulley on the corresponding end of said motor and in alignment withsaid shaft pulley, belt means connecting said pulleys to drive said saw,and strap means attached to said base to clamp said motor in its arcuatecradle surfaces at a selected position to apply tension on the belt.

2. A portable saw consisting of a base plate 1 with said second socket,a power saw mounted on said frame with the saw extending below the baseplate and in a plane disposed normal to said back plate, and a pivot rodhaving two legs disposed at right angles, one leg of said pivot rodoperating in the first socket member and the other leg operating in thesecond and third socket members.

3. A hand saw power tool consisting of a pressed metal base plate havingan upwardly extending perimetral flange, two sets of aligned arcuatecradle surfaces in oppositely disposed sections of said flange withtheir axes in parallel spaced relation, a rotary motor having arcuate 8.surfaces on the ends thereof complementary to one set of said arcuatecradle surfaces but eccentric to the axis of said motor, bearing meanssecured to the other set of arcuate cradle surfaces on one side of saidmotor, a rotary shaft in said bearing means and having one end connectedto be driven by said motor, a circular saw on the other end of saidshaft extending below said base plate, a hinge member attached to thebase plate on the other side of said motor with its axis parallelthereto, a work shoe covering the underside of the base plate and havingan upwardly extending back plate with an arcuate slot, a second hingemember mating with the first hinge member and having an adjustable clampmovable in said arcuate slot, a right angle hinge pin having one endpivotally held Within said first and second hinge members, a third hingemember attached to said work shoe in alignment with the I axis of saidarcuate slot and adjacent the saw to receive the other end of said hingepin, a second clamping plate having an arcuate slot and hinged to saidbase plate in alignment with the axis of said third hinged member, theslot in the second hinge plate having its axis in alignment with thefirst hinge members, and clamp means attached to said work shoe andoperating in the slot of the second clamping plate, whereby the Workshoe may be adjusted relative to the base plate to provide differenteffective saw cut depths at different angular positions.

ARCHER W. RICHARDS.

ERVIN J. OSTERHUS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 765,141 Killam July 12, 1904 1,323,490 Putnam Dec. 2, 19191,393,990 Ford Oct. 18, 1921 1,568,328 French Jan. 5, 1926 1,623,290Wappat Apr. 5, 1927 1,663,486 Wertz Mar. 20, 1928 2,001,823 Knowlton May21, 1935 2,204,402 Cooper June 11, 1940 2,259,092 Trebert Oct. 14, 19412,268,305 Reinhard Dec. 30, 1941 2,315,467 Wahlberg et al. Mar. 30, 1943FOREIGN PATENTS Number Country Date 736,593 France Sept. 20, 1932

